I'm curious if we see other unconformities related to other Ice Ages. If receding glaciers scraped away the earth and led to this big of a gap, shouldn't this have happened again when the glaciers receded after more recent ice ages, like in the Pleistocene?
Pleistocene glaciation in the northern hemisphere has been a lot shorter (so far) than the Cryogenian glaciations, but it is probably not a coincidence that the outline of Canada's "Precambrian shield" basically matches the outline of the Laurentide ice sheet (check out Figure 5 of the 2019 paper [1]). We're probably only talking about scraping off no more than a couple hundred meters of sedimentary rock formerly covering the shield, but that's about what you'd expect.
More broadly, as one author noted long before us [2] it turns out that most of the places on Earth where there is a lot of Precambrian crystalline basement exposed at the surface today (i.e., where later sedimentary rocks have been scraped off, one way or another) were glaciated either recently or in the Late Paleozoic Ice Age [3], which hit much of Gondwana (see also Fig S16 here [4]).
More recently, another group of researchers using thermochronology in Antarctica [5] found evidence of several kilometers of exhumation during the Late Paleozoic Ice Age, as well as perhaps 1-2 km during the last ~35 Myr of Cenozoic glaciation (n.b., Antarctica has been glaciated for a good bit longer than we've been having ice ages in the northern hemisphere).
I'm going to be a bit fanciful here, but it's a serious question. What implications does this have, if any, for the possibility of human civilizations older than currently known being completely erased by the ice? Is that plausible? How much rock would have to get scraped and pulverized into future magma to wipe out all evidence of a civilization?
> How much rock would have to get scraped and pulverized into future magma to wipe out all evidence of a civilization?
it would take a lot. Even in the snowballs, when we had ice on every continent, there are still plenty of basins (mostly at the continental margins) where syn-glacial sediments are preserved; that is in part how we know the glaciations happened. While we have maybe 1/5th as much sedimentary rock volume per unit time prior to the end of the unconformity, that still leaves a lot!
At the time of the Cryogenian, both the fossil record and DNA-based molecular clocks suggest we didn't have multicellular animal life until after at least the first (Sturtian) glaciation. And we're talking basically just sponges (porifera) at first.
Of course, it's not impossible we could have another snowball in the far future (probably unlikely for several reasons, but never say never), and the question of what that would do to the record of modern human civilization is an interesting one.
The short answer is "I don't know", but I think it would be hard to erase all traces without something a good bit more severe than the erosion that produced the Great Unconformity.
This brings us to a question I wanted to ask: Given that a lot of rock is missing from this period, how likely is it that the abruptness of the Cambrian explosion is an artifact of missing evidence? How likely is it that we would even recognize a distinct Cambrian period, if four-fifths of the Cambrian rocks were missing?
Ah, good questions. Although we are missing a lot of rock, paleontologists have spent a lot of time looking through the non-missing parts. So far, they have found a lot of really interesting things, such as the macroscopic soft-bodied fossils of the Ediacaran biota [1], but even so there's really very little in the way of shelly fossils until the Cambrian, and their appearance really does seem to be quite sudden as far as we can tell!
I’m under the impression that we’re still in the quaternary ice age. What makes a snowball impossible now? The division of the ocean in two that restricts convection and the large polar continent that provides a convenient place for ice sheets to increase the Earth’s albedo both suggest, to my admittedly limited understanding, that a severe glaciation isn’t out of the cards. I ask not to challenge but to learn.
Edit: I can’t remember the name right now, but there are also a bunch of solar cycles that affected past glaciations. I’d be grateful for information on that too.
We are still in an icehouse period, yes! However, a few things may make it a bit harder for that to develop into a full snowball, currently:
1) While having continents at the poles makes it easier to have icesheets at all, it also makes it harder for them to grow into a full snowball. This is because
a) covering the continents with ice shuts down silicate weathering (and silicate weathering consumes CO2, so that's a stabilizing negative feedback)
b) the difference in albedo between water and sea ice is greater than the difference in albedo between land and ice. So if you can get cold enough to start making sea ice at the poles, you should get a stronger positive feedback of cooling -> higher albedo -> more cooling
During the Neoproterozoic, most or all of the continents seem to have been near the equator, so silicate weathering could keep going until sea ice reached the "point of no return" of the sea ice-albedo feedback [e.g. 1]
2) The biosphere is pretty different today than it was last time we had a snowball, and there is some reason to think that evolutionary developments like land plants and pelagic calcifiers may make the climate system more stable than it was 700 million years ago.
None of that is to say it's impossible though! The solid earth acts slowly, but it's a big lever, so hypothetically if you could somehow crank silicate weathering up high enough and volcanic degassing down low enough, you could probably still in principle reach the tipping point again.
For your last question, you are probably thinking of Milankovitch cycles [2] -- those are definitely going strong as well, though generally not strong enough to get us into or out of a snowball state.
That certainly doesn't help either! To some extent though, anthropogenic emissions are dangerous more for their rate than their absolute magnitude; in the long run, once we stop emitting, silicate weathering will take back over "soon enough" -- it's just that "soon enough" in this case means ~5 myr and probably a mass extinction later.
The other one I forgot to mention is that the sun is a bit brighter now than it was 700 Myr ago (by perhaps a few percent). Go back another two or three billion years to the Archean and the difference would have been bigger -- to the point that we have some trouble explaining why there weren't a lot more snowballs back then [1]
Is it possible from geological evidence to confirm that Sun was dimmer billions years ago? I am asking as stability of Earth orbit cannot be taken for granted for such periods. For example, we could underestimate the effects of solar wind in past that could have pushed Earth, or the could be an interaction with passing close stars.
Ah, so there are many things that it is hard to be absolutely certain of in geology, but changing Earth's orbit is at least very very hard; even the kinetic energy from things like the Chixulub impact are far too small to have a significant effect. The "moon-forming impact" in the most common model of the origin of the moon might be more on the right order of magnitude, but there don't seem to have been any of those more recently than about 4.51 Ga. An astronomer could say more, but solar luminosity is also relatively well understood from studying other main-sequence stars of various ages.
The most common solutions involve high concentrations of organic greenhouse gases like methane as well as high CO2, but it's always possible there are other possibilities that have not yet been considered.
We do not have good models of the rate Sun has been losing hydrogen especially on scale of billions of years. So from that we do not have a precise answer how heavier was Sun in past. But heavier Sun implies that Earth was closer compensating for the dimmer younger Sun.
As I understand according to the current estimates this not enough to avoid the cold Earth problem, but there are way too much uncertainty. But if we do not have way to read the brightness from geology alone, that can be an answer.
I have to say I was thinking to myself this person identified as a geologist, so an event that started 200 years ago probably isn’t a major concern. In the sense of geologic timescales I mean.
Not a professional anthropologist or historian, but I do enjoy reading about it. You should be skeptical when authors/books make general claims about a large group of people. There are counterexamples, especially when writing about a long period of history, and books like these can often end up being Eurocentric.
Here are some good Reddit threads from r/AskHistorians and r/AskAnthropology, where professionals often visit, describing the flaws in Sapiens. The comments have specific examples, if you follow the links.
> Beyond that, Harari seems generally unconcerned with differentiating the experience of Western Europe from the experience of "us"- the species. This is why I can't really recommend the book, because this so thoroughly undermines his apparent goal. The very name of the book tells us that it will be a history of all of us and how we became so dominant in the world. And yet, so much of the book focuses on things that only a portion of H. sapiens ever developed, but talks about them as if they were natural developments for our species as a whole.
Sapiens is a big "picture human history" book, which is a genre which is always going to have a number of weaknesses due to the problems of trying to squelch all of human history into a single readable book with a clear thesis. The quote about the French Revolution is indeed pretty bad as a literal description of what happened during the revolution, (though I understand what he is getting at when he says it.) However, I don't think that this analysis is quite fair to Harari.
His main criticism is of Harari's "shared fiction" concept and it seems to me that he misses the point of the concept. Harari is pointing out a category of thing that really does exist in the real world, but only exists because people agree on some level to recognize its existence. Corporations (to use Harari's example) are indeed real, but they exist only because people agree they exist. If people refused to believe in IBM, for example, it would cease to exist.
I don't know if Harari is correct that this ability to embrace social realities actually constitutes a "cognitive revolution" that allowed homo sapiens to surpass other human species in a dramatic way, but I do think that it is certainly different from our ability create a word for "rock" and thereby reify rocks into existence. There's a difference between being able to create arbitrary categories for material objects in the world and being able to recognize a new category of thing through shared acceptance. I don't think that the latter is simply a consequence of our ability to use language.
Also, it's important to note that that critique is being offered by a historian but the core of the critique is philosophical (or maybe linguistic) not historical. I think the best criticism I've seen of Sapiens is that the author is a historian trying to write anthropology, but this critique of that anthropology book is also by an historian so it has the same weakness.
So, after reading those threads, my first impression is this is an ideological disagreement, but not that Harari is actually wrong in his analysis.
Ok, so I'll start with some observations on the comments themselves, and will continue to explain what really needs to be addressed in order for me to understand things better. The comments seem to dislike that this book is about the whole of humanity, written in a short book, so I would expect a simple counter to this, but I see people not having read the book in full:
QUOTE "But again, since I've yet to personally read the book rather than get second-hand info about it"
QUOTE "I've tried to read it twice and not got very far."
QUOTE "I've seen some water cooler chat about the book, but I don't personally know anyone that has read the book - like myself"
Regardless, the first link seems to contain better info on why it's wrong, with specific detailed counters, it's just that those details could still be off, but the premise could still be right... however this "benefit of the doubt", let's call it, is only given to OTHER books just not Sapiens:
QUOTE "This is why a book like 1491 has been so much more warmly received. One can undoubtedly find dozens of factual errors within. But instead of mirroring a popular inquiry born out of popular ignorance ("Why were the Americas so decisively conquered?"), it recognizes that ignorance as a problem to be solved."
First, "warmly received" is useless here, and second we can start to see the root of the disagreement... it has to do with a specific perspective of the world, and anyone going against that perspective is wrong (but of course, the reasons won't be made clear -- instead attacking mistakes, character, and credentials).
The following quote shines a light on this a bit more.
QUOTE "Some would argue that language is purely abstract- that the act of calling something a rock is what creates the rock. As much as the 'rock' exists as a physical object with observable properties, there is no natural boundary between 'rock' and 'pebble' and 'sand.' "
Ah... isn't this interesting? This is all philosophy, and I would even label Sapiens as philosophy to a great extent. These are all theories that can only be reasoned about, and thus we enter Epistemology and Ontology, and we're in a completely different territory than History. We're trying to understand ourselves in History, this is not an event, or a fact.
In conclusion, I would like a hard counter to his simple premise, which is an answer to the question, why are humans so different than the rest of the animal kingdom? (TED talk summarizes it nicely), and also, I would like to point out that the criticisms are not self-aware that they're arguing philosophical matters and instead are pretending they are countering hard historical facts, and dismissing the book on that basis.
TL;DR: why are humans so different than animals, and why is that a historical conversation, when it's really philosophy, and ultimately Harari made it simple, so there should be no need to argue around it if he's wrong in his premise.
It seems an attacker with physical access still requires your password to unlock the disk. At that point, they'd need the Yubikey to login (assuming they haven't already decrypted the disk and taken your data).
> It seems an attacker with physical access still requires your password to unlock the disk. At that point, they'd need the Yubikey to login (assuming they haven't already decrypted the disk and taken your data).
Its just PAM (pam_yubikey to be precise). If they have physical access they can edit the requirement for Yubikey in PAM.
If there's FDE (FileVault) then I don't know. But I do know the PAM configuration must be read, and is therefore in r/w. It isn't in some kind of security enclave.
If it's long and random enough to be very hard to remember, then it's MFA, in my opinion. A private key (e.g. the one used for TOTP) is nothing more than a quantity of random bits (with specific properties, grant you). I'll give you that the output is certainly reusable for a statically stored key, but you're still adding a second factor that, barring some alternate attack like keylogging, still adds security beyond a password.
Hmm, it's unfortunate that this is being shut down. If you're looking for alternatives, I've been using the New York Times app, CNN, and Buzzfeed News. You need to deal with some annoying notifications (for example, CNN sent me a "Hero of the Year" notification today), but it's better than nothing.
I'm already aware of the content of ever MSM feed, no matter the platform. At least 50% is complete opinion pieces questioning every choice and sentence spoke by the POTUS-elect, at least one article giving false hope that the election could still be over-turned, an article about how hot Ryan Reynolds or Ryan Gosling is, an article that is just a video (or recap) of SNL mocking said POTUS elect, an extremely vague article about why the Obama's where so amazing, and one buried article about something new and interesting that most people should be aware of.
Well, check out basically any news source besides Fox, which I don't care for either, and tell me how I'm wrong. I'm not a Trump supporter, but MSM has become identical to Facebook news feed. It's popular opinions dressed up as news. I don't feel like it's informing me of much.
They're not going to get much traction with the Fake News narrative if they don't enact some real change on their part. If I'm wrong and there's a news source out there that isn't comprised of this, I'd appreciate you guys pointing me to it.
I think funding mass media is less interesting than finding a way to have sustainable investigative journalism, both at the local and national levels. Investigative journalism, especially at the local level, has been hit hard by local newspapers getting shut down and the media forced to either pull out of unprofitable areas or focus on money-making ventures. Most media outlets are not the New York Times or Washington Post; they can't afford to send reporters out for months to put together enough evidence to run a long-form story. The end result though is that most media outlets focus on what attracts viewers and makes them money: partisan commentary, stories that spread FUD, and feel-good stories. The end result is that government and business officials can run amok without anyone holding them accountable.
Let mass media focus on general-interest stories and slowly become reality TV for reality. If we instead focus on investigative journalism, we'll have a way for journalists to provide unbiased content without depending on the mass media to provide the funding to do so.
So long as journalists are paid with ad dollars, content will always trend towards the lowest common denominator.
This applies to all media in general; but there really needs to be a better metric for quantifying impact than clicks. If writers, etc. are rewarded for advancing knowledge, then many many more people would be enabled to do so.
Hell, perhaps we don't even need a new metic, and instead just subsidize everyone with UBI. Those who provide long-term value will outweigh those who only consume.
It's a good question, and really, the crux of the whole issue. I don't have evidence, just belief... The value of incremental knowledge, and of lives lived without scarcity consciousness, when measured across large enough time-scale, could have exponential impact on humanity (snowball effect). Whereas the cost of UBI, while large, is relatively linear.
Hopefully, some of the experiments on UBI can start to provide the evidence.
I suppose what I'm asking is are there are enough resources to allow UBI right now with a major chunk of the labor force (and subsequently tax income) disappearing?
Sustainable investigative journalism is most likely going to solve itself by technologies and access to information and so it makes little sense to want to focus on that as a business category IMO. Making it sustainable is a byproduct of the technologies, tools and legislative work we develop.
In fact one of the best tools is already here we are using it right now. It's never been as cheap to do as it is right now.
> Sustainable investigative journalism is most likely going to solve itself
This sounds like your saying the business model for investigative journalism is obvious and easy.
> People in general don't pay for investigative journalism and so it's never going to be a business category in itself
This shows that you actually don't think it's solvable / there is no business model. If it's being done as charity or thankless hard work then I don't think that's solved.
Perhaps I wasn't clear enough so for that, I apologies.
So what I am basically saying is that investigative journalism IS already sustainable it's just not a business.
It's if anything a process or a number of very loosely defined processes if even that.
The process is going to cost whatever it cost to investigate whatever it is you want to investigate and the only way to make it "sustainable" (cheaper) is through the development of other areas which has nothing to do with that process.
The link I reference shows a pretty simple, cheap and powerful form of investigative journalism (he more or proved Theranos was not working).
If you want to break into the US military and steal their secrets it's going to take your whisteblowers to get the information.
So trying to put it into a business context is misleading as it's just really a broad area of snooping around hoping to find some dirt.
It's a very interesting problem. Look, for example, at the large and provocative studies of Herman and Chomsky [1,2] and trying to remove the bias that exists in mass media, especially the self censorship. There must be many studies of these problems that are more recent [3] and include the role of the internet.
I can only see tax dollars funding this approach - the BBC is the clear up on a pedestal example of this, and sometimes you have to say, the market sucks at fixing some issues.
Exactly. Everyone in the U.S. gets taxed a couple bucks a month, and it gets apportioned among independent (not advertising supported) content creators based on page views, ratings, and whatever other factors. This is probably the only way to fix the problem.
State run media is actually very good at solving the problems you find aggravating.
99% of useful news has nothing to do with the things you imagine state run news will be bad at informing you about. It is a world without sensational click bait. The 1% of the time some journalist goes missing, well thats what WeChat is for.
The Voice of America RSS feeds [1] are mostly clickbait-free. It's officially the position of the US Government, but has a long tradition of being neutral to the point of blandness. To try to drum up more interest, there are now some more tabloid-like feeds, such as "VOA Fast Five".
The VOA's judgment on what's important is a lot better than most of the US media, where click-through rates seem to determine placement.
I agree 100%. I actually have worried about this problem for a long time and I have come up with quite a lot of clever ideas (well I think they are clever) to solve this problem. Pity I don't have any time :(
The ideas are a bit too long for a post here on HN, but if people are serious about wanting to pursue a startup in this area then get in contact with me [1].
I know there are lots of people wanting to start a startup who feel they don’t have any good ideas so if this is an area you are passionate about then I am happy to talk. I am in the lucky position of having the financial resources to fund a new startup, but because I am busy running my own business, I just don't have the time to do it myself. When I was younger I had lots of time and no money, now I am older I have the lots of money and no time :(
1. I am pretty easy to find and do a background check on.
I'd be very interested! This is a field that I recently became extremely interested in and even met up with my lawyer earlier today to discuss a bulk FOIA research project. I left a comment on your blog with contact info if you're interested in talking. :)
At the big tech firm I work at, there's a best practice where any database (whether that's a traditional RDBMS or a NoSQL client) is abstracted away by a microservice with a defined API, and every other application that wants to get that data needs to interact with the microservice. That way, the database schema can change without it affecting multiple applications. There's still the traditional mismatch between ORM and database, but doesn't feel as painful because only a single application is using that data, and that application can have special knowledge of the persistence layer underneath (meaning, use database hints if necessary, defer to raw SQL, etc.)
We have decades of research into filtering, joining, and aggregating across a complex set of tables and views. With microservices you have to roll your own query planning and stream all the intermediate results on the wire even when you're throwing away most of them.
The thing is, letting the system handle it isn't good enough. We have decades of research into this stuff, so 90% of the time the database gets it right - but the interface for explicitly taking control when the DB gets it wrong is black magic at best. The value of having an exposed representation of filtering/joining/aggregation in a general-purpose programming language where you can interact with it is big enough to outweigh that of a database that can do it for you most of the time.
Unfortunately, SQL servers aren't generally scalable. Offloading joins and aggregation onto (inexpensive) app servers can increase over all system performance, despite lack of advanced query planning.
Bollocks. SQL scales fine unless you are stupid in the way you use it. All the crap performance I have seen in the last couple of years have been from doing crap like you suggest - doing joins and aggregation at the application level. Our front page currently makes over 1000 database calls because of this sort of nonsense.
That kind of sounds like a microservices anti-pattern in disguise. Its thought by many to be bad practice for microservices to share a common database. But that's pretty much what you're doing, but just with an API instead of jdbc for the access.
Yup, definitely aiming to solve the same problem. My hope though is that by making it web based (and perhaps providing an app) I can lure some businesses into using it to track all their incoming packages, which they wouldn't want to do with a phone app exclusively.
What fascinates me is how close this synthetic filesystem is to making REST calls with a small client library. All your application needs to know is the path to call and what HTTP verb to use. Even the way the author introduces versioning sounds familiar: using a versioning file is similar to having a version at the beginning of your URL.
I appreciate how good architectures all resemble each other at some point, with only the transport layers differing between applications.
REST is just CRUD over HTTP. The file interface and Unix everything-is-a-file concept are one of the earliest well-defined CRUD interfaces in computing. The author (and Plan 9) are taking these concepts to their logical conclusion.
In order not to get into trouble with the SEC, wouldn't Icahn have had to issued this press release alerting investors to look at his Twitter account before he tweeted? Seems like it happened the other way around, which leaves plenty of leeway for screwy trading.
